It is often desirable to control the amount of lighting in an area (e.g., roads, buildings) in order to conserve energy.
Some systems control the amount of lighting based on historical traffic statistics, i.e., increasing lighting during times that are historically busy (e.g., evening rush hours) and reducing lighting during times that are historically not busy (i.e., non-rush hours).
Some systems control the amount of lighting by reducing lighting unless motion sensors detect the presence of traffic (e.g., vehicle).